The present invention relates generally to magnetic circuit components and more particularly to magnetic components for mounting on a circuit board housed within a full or partial enclosure. The present invention also relates to electronic devices and associated methods of manufacturing enclosed electronic devices.
Magnetic components including a magnetically permeable core and one or more conductive windings positioned near the core are known in the art. Such components are used in conventional inductors and transformers in a variety of electronic applications. Magnetic components of this type can generally be configured for surface mounting on a circuit board for use in an electrical circuit. Common applications for such devices include, inter alia, power supplies, power converters and power regulators. These devices can be used, for example, in electric lighting applications for controlling or regulating electrical power delivered to an electrical load such as a lamp, bulb or LED. Typically, in these applications, the circuit board and the electronic components disposed on the circuit board are housed within an enclosure.
Conventional magnetic components configured for mounting on a circuit board generally include a core structure having one or more core legs extending outward from a core body. Each core leg has a leg height, a leg length and a leg width. A conductive winding including one or more turns of a conductive wire can be positioned around a core leg. In some conventional applications, primary and secondary windings are positioned around a core leg to form a transformer. The conductive winding or windings can be positioned on a bobbin structure, or coil former, in some applications. The bobbin structure can include an axial opening, and a core leg can be inserted into the axial opening such that the bobbin structure and the conductive coil both surround the core leg.
Because magnetic circuit components in electronic devices generate heat during use, it is generally desirable to dissipate heat away from such components to ensure proper circuit operation and to reduce the risk of component failure or fire inside the enclosure. Additionally, in many applications, a magnetic component such as an inductor or transformer forms the largest circuit component mounted on a circuit board in an electronic device. Thus, any enclosure formed to surround the circuit board must have interior dimensions sufficient to accommodate the size of the tallest circuit component, i.e. the transformer or inductor. Additionally, the growing trend of miniaturization in the electronics industry seeks to reduce electronic device profile, resulting in narrow gaps between interior enclosure walls and the surfaces of magnetic components mounted on the circuit board housed within the enclosure. However, the goal of miniaturizing electronic devices by reducing the space between components and enclosure walls can make the additional goal of heat dissipation away from enclosed magnetic components more difficult to achieve.
Others have tried to address the problem of dissipating heat from conventional magnetic components by providing a gap filler material between the magnetic component and the enclosure wall. The gap filler material allows the enclosure wall to act as a thermal bridge or heat sink to dissipate heat away from the magnetic component. Heat generated in the magnetic component transfers from the core, bobbin or winding through the gap filler into the enclosure wall. From the enclosure wall, the heat can be further dissipated to the surrounding environment or can be passed to heat dissipation structures such as cooling fins. The heat can then be removed from the enclosure or cooling fins by natural or forced convection and/or radiation to the surrounding environment.
Heat flux from the magnetic core to the gap filler is partially a function of the surface area in contact between the gap filler and the magnetic component. One problem associated with conventional magnetic components is inadequate surface area contact between the gap-filler and the magnetic component for optimal heat flux from the magnetic component.
Another problem associated with conventional magnetic components is a tendency of the gap filler to become locally separated from the surface of the magnetic component over time. When surface separation between the gap filler and the magnetic component occurs, heat dissipation is greatly diminished.
What is needed, then, are improvements in the devices and associated methods for dissipating heat from magnetic components in electric circuits.